1. Preheat the oven to 400 degrees F. Start cooking the rice according to package directions. I used a rice steamer, with 1 1/2 cups water and the boullion cubes.
2. Put a little oil or butter on the cut sides of squash and in a casserole dish, then put them cut side down in the dish. Roast for 1 hour, or until they collapse easily when pushed with a wooden spoon.
3. Heat the olive oil in a frying pan on medium heat. Put in the onion and saute it for about 3 minutes, then add the celery and saute it for around 2 more, then add the walnuts and saute a little longer until the onion is transluscent, the celery is on the soft side, and the walnuts are a little toasted.
4. If the rice isn't done yet, turn off the flame on the onion pan and stir in the vinegar, tarragon, sage, garlic, salt, and pepper. If the rice is done, add that to the onion pan with vinegar and spices. Continue heating it a little to meld the flavors. When squash is done, spoon the rice mixture into the cavity and voila!
I had it with unchicken patties, country-style dijon mustard, and steamed corn-on-the-cob as a happy fall equinox meal. It was only me and my boyfriend, so I saved 1/2 the rice and only cooked 1 squash.